1. The Field of the Invention
The present invention relates generally to keypad devices, and more particularly, but not necessarily entirely, to a switch matrix which allows the use of variable key positions and key sizes on the keypad.
2. Description of Related Art
It is common practice to provide keypads consisting of one or more keys arranged for entry of data or performing functions such as activating switches. Keypads are used for various types of electronic devices such as user interfaces for home automation and security systems, calculators, telephones, etc. Keypads commonly include an assembly of various parts maintained in a housing.
For example, FIG. 1 shows a keypad, generally indicated at 2, known in the art for use as a primary control point for automation systems used in areas such as homes, businesses, boats, yachts, motor homes and busses. The keypad 2 includes a plurality of keys 8 which can be depressed to control systems such as lighting, security, audio visual and heating/cooling for example. The keys 8 are connected to electronic circuitry which is contained in a housing 4. The keys 8 are fixed in place by an attaching plate 6 so as to be non-removable from the keypad 2. The attaching plate 6 has apertures 7 through which the keys 8 protrude. The apertures 7 are sized and shaped to accommodate keys 8 of a particular size and shape. Therefore, a different attaching plate 6 is required for each size and shape of keys 8 used for the keypad 2. Furthermore, the location of the keys 8 is confined to the locations of the apertures 7. Therefore, a different attaching plate 6 must be used for different configurations of the keys 8. Moreover, if any of the keys 8 become damaged or require replacement, the entire keypad 2 must be replaced or the attaching plate 6 must be removed. Removal of the attaching plate 6 is a difficult task which may require the services of a professional or use of specialized equipment since the attaching plate 6 is fixed to the housing 4 and is not designed to be easily removed without damaging the attaching plate 6 or the housing 4.
The prior art is thus characterized by several disadvantages that are addressed by the present invention. The present invention minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.
In view of the foregoing state of the art, it would be an advancement in the art to provide a switch matrix which is capable of being used with keys of different sizes and shapes. It would be a further advancement in the art to provide a switch matrix which allows the keys to be arranged in different configurations using differing numbers of keys. It would also be an advancement in the art to provide a switch matrix which allows the keys to be easily installed and replaced without damaging the matrix.
In view of the above described state of the art, the present invention seeks to realize one or more of the following objects and advantages.
It is a primary object of the present invention to provide a switch matrix which is simple in design and manufacture.
It is another object of the present invention to provide such a switch matrix which is capable of being used with keys of different sizes and shapes.
It is a further object of the present invention, in accordance with one aspect thereof, to provide a switch matrix which allows the keys to be arranged in different configurations using differing numbers of keys.
It is an additional object of the invention, in accordance with one aspect thereof, to provide a switch matrix which allows the keys to be easily installed and replaced without damaging the matrix.
The above objects and others not specifically recited are realized in a specific illustrative embodiment of a switch matrix device. The device preferably includes a support frame including at least one longitudinal member and at least one lateral member substantially perpendicular to the longitudinal member. The switch matrix also preferably includes a grid of key positioning members disposed on the support frame in a series of rows and columns. The key positioning members each preferably include a first cantilever and a second cantilever. The second cantilever preferably includes a pair of arms. An attaching end of the first cantilever is preferably attached to a free end of the second cantilever such that the first cantilever extends parallel to the second cantilever between the pair of arms and towards the fixed end of the second cantilever. The first cantilever also preferably has a key attaching means for removably attaching a key to the key positioning member. The key attaching means preferably includes a knob which is adapted to be fitted into an opening in the keys with a corresponding shape to form a compression fit between the key and the attaching means. This allows the keys to be removably attached to the switch matrix so that keys of differing sizes and shapes may be utilized. The key positioning members are preferably configured to deflect when the key is depressed to activate a switch with a switch activating protrusion which is preferably disposed on the opposite side of the first cantilever from the key attaching means. The keys can preferably be selectively attached to the key positioning members in various configurations suited for a particular application.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the invention without undue experimentation. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.